Conventional anti-tank projectiles are designed as subcaliber shells which are provided with a sabot that is discarded in flight, not without danger to friendly personnel nearby.
It has already been proposed to provide projectiles of this type with a casing within which a warhead is axially slidable between a forward and a rearward position (see U.S. Pat. No. 2,684,629); in its forward position, which the warhead occupies during firing, an annular channel formed between it and the surrounding casing is blocked to prevent the escape of combustion gases generated by the gun blast. In flight, the resistance of the ambient air represses the warhead into its rearward position in which air entering the channel from the front reaches a charge in a combustion chamber forming part of that channel. U.S. Pat. No. 2,989,922 discloses a similar arrangement wherein, however, the warhead on firing closes the rear end of the channel which is reopened in flight by the relative motion of the warhead and the casing to facilitate the discharge of thrust gases developed in the combustion chamber.